Definition and Solar Context
Solar irradiance is the measure of electromagnetic radiation power received from the sun per unit area at a given location. It is a foundational input in solar energy production modeling and serves as the primary resource variable in the SunScore™ Projection Engine.
GetSunScore references solar irradiance data from the National Renewable Energy Laboratory's (NREL) National Solar Radiation Database (NSRDB) to generate georeferenced production estimates across Texas.
What Does Solar Irradiance Mean?
Solar irradiance is quantified in watts per square meter (W/m²) and represents the instantaneous power density of solar radiation striking a surface. In solar energy analysis, the relevant irradiance metric for system performance modeling is Global Horizontal Irradiance (GHI).
Annual cumulative irradiance — expressed in kilowatt-hours per square meter per year (kWh/m²/year) — is used to estimate how much energy a photovoltaic system can be expected to produce over a given period.
Why Irradiance Matters in Solar Savings Modeling
Solar irradiance is the primary production-side variable in solar savings modeling. The SunScore™ Projection Engine translates annual irradiance values into estimated annual energy production figures, which are then applied against local utility rate structures.
Higher irradiance values produce higher estimated energy yields, which in turn generate larger estimated savings figures. GetSunScore uses location-specific irradiance data to ensure projections reflect actual geographic conditions rather than regional averages.
How Solar Irradiance Applies in Texas
Texas ranks among the highest-irradiance states in the continental United States. Western Texas — including the Permian Basin and Trans-Pecos regions — receives some of the highest annual GHI values in the country.
The SunScore™ Projection Engine applies NREL NSRDB data at the ZIP code level across Texas to capture regional irradiance variation. ERCOT's grid structure enables distributed solar generation across most of the state, making irradiance-to-savings modeling widely applicable.
Frequently Asked Questions
Solar irradiance measures the power of sunlight reaching a specific location. Higher irradiance means more solar energy available for conversion. It is the foundational production variable in any solar savings estimate.
The SunScore™ Projection Engine applies NREL NSRDB irradiance data at the ZIP code level to estimate annual solar energy production for a modeled system. This production estimate is then applied against local utility rates to generate an estimated savings range.
Yes. Western Texas receives significantly higher annual solar irradiance than the Houston or DFW areas. The SunScore™ Projection Engine accounts for this geographic variation using location-specific NREL data rather than statewide averages.
Not exactly. Irradiance is a power measurement (W/m²), while Peak Sun Hours represent the equivalent number of hours per day at peak irradiance (1,000 W/m²). See the Peak Sun Hours glossary entry for a detailed explanation of how these concepts relate.
GetSunScore references NREL's National Solar Radiation Database (NSRDB), a publicly available georeferenced dataset, as the primary irradiance source for the SunScore™ Projection Engine.
All irradiance data sourced from NREL NSRDB. Projections referenced on this page are modeled scenarios based on publicly available datasets including NREL, EIA, and Texas utility rate filings (reference year: 2024). Results are non-binding estimates.